In modern engines, a rail pressure, which is adjusted by a pressure-control valve and monitored by a rail-pressure sensor, is an important parameter for influencing and/or regulating the power output of the engine. In known methods heretofore, rail-pressure sensors RPS having an analog interface were utilized. In the past, the data of RP-sensors were a favorite target of manipulation, so-called tuning attacks. Two important attack scenarios are:    1. Replacement of the RP-sensor by a similar model having different characteristic properties.    2. Manipulation of the analog pressure data on the transmission link, for instance, by inserting a resistor (→lower voltage→feigned lower pressure).
Future rail-pressure sensors can be equipped with a digital PSI5-interface. In this connection, one essential requirement is that there should be indisputably strong information as to whether manipulation was carried out.
Protection goal 1 (preventing the replacement of the sensor) may be achieved by “authentication” of the sensor at the control unit. For example, challenge-response protocols are used for this purpose In the related art, unilateral authentication methods according to “ISO/IEC 9798-2, Information technology—Security Techniques—Entity Authentication—Part 2 Mechanisms using symmetric encipherment algorithms” ISO/IEC, 1999 are often used for the authentication, either as two-pass unilateral authentication protocol with nonces or as one-pass unilateral authentication protocol with time stamps/sequence counters.
Protection goal 2 (recognition of manipulation of the sensor data) may be achieved by integrity-protection methods. In the related art, standardized cryptographic methods, for instance, message authentication codes or digital signatures, e.g., “ISO/TEC 9797-1. Information technology—Security techniques—Message Authentication Codes (MACs)—Part 1: Mechanisms using a block cipher. ISO/IEC, 1999” or “ISO/IEC 9797-2. Information technology—Security techniques—Message Authentication Codes (MACs)—Part 2: Mechanisms using a dedicated hash-function. ISO/IEC, 2002” are used for protecting the integrity of the data.
Moreover, to prevent replay attacks, according to the related art, additional so-called time-variant parameters (random numbers, time stamps, sequence numbers) are added to the data to be safeguarded by integrity protection.